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authorIan Kent <raven@themaw.net>2021-07-16 17:28:18 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2021-07-27 09:29:14 +0200
commit895adbec302e92086359e6fd92611ac3be6d92c3 (patch)
treef2b672c39511d1918b8ff32bfd6e8038d84c3f15 /include/linux/kernfs.h
parentbdac4d8abbfc239886103f7c6ee03abb8011a008 (diff)
kernfs: add a revision to identify directory node changes
Add a revision counter to kernfs directory nodes so it can be used to detect if a directory node has changed during negative dentry revalidation. There's an assumption that sizeof(unsigned long) <= sizeof(pointer) on all architectures and as far as I know that assumption holds. So adding a revision counter to the struct kernfs_elem_dir variant of the kernfs_node type union won't increase the size of the kernfs_node struct. This is because struct kernfs_elem_dir is at least sizeof(pointer) smaller than the largest union variant. It's tempting to make the revision counter a u64 but that would increase the size of kernfs_node on archs where sizeof(pointer) is smaller than the revision counter. Reviewed-by: Miklos Szeredi <mszeredi@redhat.com> Signed-off-by: Ian Kent <raven@themaw.net> Link: https://lore.kernel.org/r/162642769895.63632.8356662784964509867.stgit@web.messagingengine.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/linux/kernfs.h')
-rw-r--r--include/linux/kernfs.h5
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 9e8ca8743c26..d68b4ad09573 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -98,6 +98,11 @@ struct kernfs_elem_dir {
* better directly in kernfs_node but is here to save space.
*/
struct kernfs_root *root;
+ /*
+ * Monotonic revision counter, used to identify if a directory
+ * node has changed during negative dentry revalidation.
+ */
+ unsigned long rev;
};
struct kernfs_elem_symlink {